Magnesium alloy is light, has high strength, and is recyclable, so it is widely used in automobiles and electronics. However, because the magnesium alloy is reactive and has poor corrosion resistance, there is a need to form a protective film on a surface of the magnesium alloy.
The conventional method for forming a chemical conversion film on the surface of the magnesium alloy is a conversion treating method, in order to enhance a corrosion resistance of the magnesium alloy, and to enhance adhesion of the surface thereof with a coating layer. When the magnesium alloy is used in a housing of a mobile phone or other electronic communication device, the resistance of the chemical conversion film reflects electromagnetic shielding of the assembly. For example, the electromagnetic shielding of the assembly is poor when the resistance is too high. However, the resistance of the chemical conversion film made by the conventional conversion treating method is generally higher, and it is difficult to meet the needs of the electronic communication device.